Surface inspection based on machine vision has been widely used for controlling the surface quantity of various products. For example, the quality of wood, steel, wafer, ceramic, textile and even the surface of an agricultural product may be inspected by optical surface inspection.
At present, touch panels tend to be designed with optimized, personalized and intuitive operations and controls to provide a convenient use, so that the touch panels can be applied extensively in various electric and electronic products such as personal computer, Smartphone, cashier machine, automatic transfer machine (ATM), and electric appliance. The quality of the touch panel directly affects the overall appearance quality and quality of an electric appliance or product as well as the yield and profit of related manufacturers. Therefore, the manufacturers demand a very high quality of the touch panels. Since a sensing circuit is installed in the touch panel, therefore if the touch panel has particles, scratches, fibers or dirt on its surface, then the effect of the sensing circuit will be affected adversely. Now, the defect detection has become one of the important and mostly needed processes in the production of the touch panels.
With reference to FIG. 1 for a spectral analysis applied extensively in conventional automatic optical inspections (AOI), an energy spectrum 20 as shown in FIG. 1(b) is obtained after performing the Fast Fourier Transform (FFT) of a touch panel 10 as depicted in FIG. 1(a) and provided for observing a major portion of energy concentrated at four directional lines including a horizontal line, a vertical line and two diagonals, wherein the angle of the diagonal varies with various different structures of circuits, and the angle of the diagonal may be estimated by the largest protruding portion of the energy spectrum 20 as shown in FIG. 1(c), and the angle of the diagonal is approximately equal to 31 degrees, and narrow stop-bands of the aforementioned four directional lines are used for the notch filtering of the energy spectrum 20 as shown in FIG. 1(b), and a reconstructed image 30 as shown in FIG. 1(d) is obtained after performing the Inverse Fast Fourier Transform (FFT). However, most circuits are eliminated while the non-circuits are also eliminated as well, and thus causing difficult distinction and complicated design of the products using notch filtering. Obviously, the spectral analysis is not an effective method for inspecting the touch panel 10.
Therefore, another automatic optical inspection method using Computer Aided Design (CAD) for drawing figures and making marks on the figures of a desired testing touch panel is available, and CAD drawings require the calibration of a camera to eliminate the distortion of the figures before the expected drawing effect can be achieved. However, the calibration of the camera incurs additional development work and cost. For high inspection efficiency, the equipment cost will be very high.
In view of the aforementioned problems, the inventor of the present invention based on years of experience in the related industry to conduct extensive researches and experiments, and finally designed an automatic optical inspection method to solve the problems of the prior art.